The fiber orientation of paper corresponds to the chain direction of molecules forming fiber, and is closely related with curling, torsion, inclination of NIP (Non-Impact Printer) paper and the like. Standards in fiber orientation are becoming strict particularly in these several years, and several types of measuring methods have been employed. There are a water diffusion method, a dynamic rupture intensity method, an ultrasonic method, a microwave method and the like as such measuring methods, and the correspondence between operations on a wire part and the orientation is substantially being elucidated at present.
On the other hand, in the case of a polymer film, that forming the film is not fiber, and anisotropy of the arrangement of molecular chains can be grasped as the anisotropy of various physical properties, for example, optical, electrical and mechanical intensity and the like. Therefore, inclusive of paper, polymer film and the like, the orientation can be collectively grasped as the anisotropy (molecular orientation) of the arrangement of molecular chains.
It is general that a solid polymer has orientation in the process where molecular chains are solidified from a fluidized state due to the shape thereof. Due to the orientation, anisotropy appears in a dynamic, thermal, optical or electromagnetic physical property. Consequently, for example, anisotropy of the modulus of elasticity, anisotropy of the ratio of heat contraction or the like, takes place to cause various problems in quality.
As methods of measuring such anisotropy, an X-ray diffraction method, an infrared polarization method, a fluorescence polarization method, a birefringence method, an ultrasonic method, a microwave method and the like are employed.
Among these methods, the X-ray diffraction method and the fluorescence polarization method require time and labor for measurement, while measurement is difficult in relation to a thick sample in the infrared polarization method. The birefringence method is a method of optically measuring anisotropy by utilizing a refraction phenomenon based on anisotropy of a refraction index, and an opaque sample cannot be measured since transparency with respect to visible light or near infrared light is required for measurement. The ultrasonic method is of a contact type and hence unsuitable for a moving sample.
A method employing resonance of a microwave utilizes anisotropy of a dielectric constant The dielectric constant has a constant relation also with a refractive index. The method employing a microwave is utilized for molecular orientation measurement regardless of presence/absence of optical transparency inclusive of paper and a polymer film.
FIG. 1 illustrates the principle of a conventional orientation meter employing a microwave cavity resonator. It comprises a microwave introduction part 2 on one end portion and a microwave detection part 4 on another end portion. The part between these end portions defines a microwave resonator 6 formed by a waveguide having a constant electric field vibrational direction. The resonator 6 is provided with a slit 8 in a direction perpendicularly crossing the axis of the resonator 6 on the position of a loop part of a standing wave. A sample 10 is arranged in the slit 8, a microwave is introduced from the microwave introduction part 2, and the microwave intensity is detected with the microwave detection part 4. The sample 10 is rotated around the axis of the resonator 6, and the intensity of the transmitted microwave is detected every rotational angle for obtaining the orientation pattern. It is also possible to obtain a dielectric constant pattern by obtaining the dielectric constant every rotational angle position from deviation between the resonance frequency when arranging the sample 10 in the slit 10 and the resonance frequency when arranging no sample.
As a method of measuring the dielectric constant with a microwave, that shown in FIG. 2 is proposed (refer to Japanese Utility Model Laying-Open Gazette Jitsu Kai Hei 3-70368). There, it comprises a pair of dielectric resonators 12a and 12b opposite to each other through a sample 10. A pair of terminals 14a and 14b oppositely arranged through the dielectric resonator 12a are provided on side portions of one dielectric resonator 12a. An electric field vector having one direction parallel to the plane of the sample 10 is generated in the dielectric resonators 12a and 12b by these terminals 14a and 14b, for measuring the dielectric constant from the resonance characteristics thereof. Here, the terminals 14a and 14b are loop-like. It is also possible to comprise a plurality of pairs of terminals 14a and 14b and measure dielectric anisotropy of the sample by switching operations thereof.
In the measuring instrument shown in FIG. 1 or FIG. 2, cavity resonators or dielectric resonators are oppositely arranged on both sides through the sample 10, and hence the shape of the measured sample 10 is limited to a sheet-like one.
Accordingly, a first object of the present invention is to make it possible to measure dielectric anisotropy not only in a sheet-like sample but also in a sample such as a stereoscopic molding.
An electric field vector in an in-sample plane required is desirably more uniform during measuring the dielectric anisotropy.
While the terminals 14a and 14b are loop-like in the measuring instrument shown in FIG. 2, a second object of the present invention is to find a terminal shape which can further attain uniformity of an electric field vector than the loop-like terminal and improve sensitivity of dielectric anisotropy measurement.